1. Field of the Invention
This invention relates to improvements in fluid valves, especially butterfly valves which have valve members secured to a rotatable shaft and extend across a tapered fluid passage through a valve housing.
2. Description of the Prior Art
A butterfly valve typically has a valve housing provided with a fluid passage therethrough, the fluid passage being circular in cross section and having a tapered surface for engagement by a rotatable, disk-shaped valve member. The valve member is located in the fluid passage so that its resilient O-ring seal, usually on the outer periphery thereof, is movable into sealing engagement with the tapered surface when the valve member is closed, thereby forming a positive seal because the pressure side of the fluid flowing through the passage will be upstream of the largest diameter part of the tapered surface. This pressure causes the valve member to wedge tightly against the tapered surface, thereby enhancing the seal between the valve member and the valve body.
The shaft of a conventional butterfly valve of the type described passes through a first hole on one side of the passage and into a second hole on the opposite side of the passage. These holes must be drilled in one operation by directing a drill radially or diametrically through the valve body to form the first hole, then across the passage and back into the valve body to form the second hole. As the drill enters the drill body to form the second hole, the drill engages the tapered surface of the valve body and, as it does so, the drill has a tendency to drift laterally or axially of the passage toward the larger end of the passage. The hole may, as a result, be inaccurately aligned with the first hole, causing misalignment of the shaft when the shaft is placed in the two holes. This misalignment shifts the shaft laterally and causes the valve member secured to the shaft to be at the wrong location in the valve body with respect to the location at which the valve member properly engages the tapered surface when the valve member is closed. Serious sealing problems arise if the shaft is misaligned. Usually, the valve body must be thrown away or used as scrap because of the misaligned holes.
Because of the aforesaid problem, a need exists for an improved valve body which has no shaft misalignment problem so that the proper sealing action will occur when the valve member is moved to its closed position. The present invention satisfies this need.